Hi there,
Beannie, I read your post and couldn't help but notice that I have been having the same concern. I have not been diagnosed with M.S. either, instead I am told I have silent migraine, or vestibular migraine and all the neurological symptoms. But I am not so sure...
And lately, I have been coughing and it feels like I have something 'catching' in my throat when I swallow. And my x-ray came out fine too. Weird. It's very scary to feel a symptom and not know where it's coming from.